1. Technical Field
The present invention relates to a projector.
2. Related Art
In the past, there has been known a projector, which is provided with a light source, a light modulation device for modulating the light emitted from the light source in accordance with image information, and a projection optical system for projecting the light modulated by the light modulation device, and projects an image on a projection surface such as a screen. Further, there has been proposed a projector, which uses a discharge lamp as a light source and is capable of projecting an image while changing the posture (see, e.g., JP-A-2-230288 (Document 1)).
The projector (the projection liquid crystal display device) described in Document 1 is provided with a light source section including a discharge lamp, a modulation device adapted to modulate the light from the light source section, a projection optical device adapted to project the light thus modulated by the modulation device, and a projection direction changing device.
The discharge lamp has a pair of electrodes, wherein the axis along which the voltage is applied to the pair of electrodes (hereinafter referred to as a voltage applying axis) is perpendicular to the optical axis of the projection optical device, and by applying the voltage between the pair of electrodes, the discharge lamp emits light. Further, the projector is configured so as to be able to perform projection even if the angle of the optical axis of the projection optical device with respect to the installation surface is changed in the state in which the voltage applying axis is always kept horizontal.
However, in the projector described in Document 1, in the posture in which the voltage applying axis of the discharge lamp is oblique to the horizontal plane, namely the posture in which the voltage applying axis extends along the vertical direction, for example, the discharge lamp becomes deteriorated. Specifically, in the discharge lamp, which emits light due to the arc discharge generated between the pair of electrodes, there occurs convection in the discharge space due to the occurrence of the arc discharge, and the upper side in the vertical direction becomes higher in temperature than the lower side due to the convection. In other words, compared to the case in which the voltage applying axis is horizontal, the electrode located on the upper side becomes higher in temperature, and the electrode located on the lower side becomes lower in temperature. Therefore, in the discharge lamp, a drop in luminance, a flicker, and so on occur due to excessive melting of the electrode excessively raised in temperature, instability in discharge in the electrode excessively lowered in temperature, and so on.
Therefore, although in recent years, a projector, which can perform projection even in the posture in which the voltage applying axis of the discharge lamp is oblique to the horizontal plane has been demanded in order to broaden the scene of use of projectors, in the projector described in Document 1, there is a problem that the discharge lamp becomes deteriorated in the posture in which the voltage applying axis is oblique to the horizontal plane.